But Vertex Inc., which calculates sales tax for Internet sellers, reports that the average general sales tax rate nationwide reached 8.629% at the end of 2009, the highest since the Berwyn, Pa., company started tracking data in 1982. That was up a nickel on a taxable $100 purchase from a year earlier and up nearly 40 cents for the decade. The highest sales tax rate in the country now stands at 12%.

During 2009 seven states and the District of Columbia raised sales tax rates, with one jurisdiction–North Carolina–actually doing it twice. Only four states hiked rates in 2008 and only one in 2007. Given state budget problems, the 2009 state sales tax increases aren’t surprising. States have also been raising income tax rates on the wealthyand on corporations and boosting excise taxes on alcohol and tobacco. With states now facing record budget shortfalls, more tax increases seem likely.

State level sales tax generally accounts for only about two-thirds of the total sales tax bill. The rest comes from levies assessed by counties, municipalities, Indian tribes and special-purpose taxing districts funding mass transit, urban renewal and even stadiums. Among lower level jurisdictions such as counties and towns, Vertex counted 649 new or increased sales tax rates during 2009 and just 192 reductions.

The result is a wide range of combined sales tax rates across the country. At the bottom: 0%, found in all of Delaware and New Hampshire, and most of Montana, Oregon and Alaska. The country’s highest rate now is 12%, in the tiny portion of tiny Arab, Ala., (population 7,500) sticking into Cullman County. The rest of the northern Alabama town, in no-sales-tax Marshall County, pays just 8%.

In Arizona, voters will go to the polls May 18 to pass judgment on a 1% rise in the state’s 5.6% rate for three years. If approved, the rate in Phoenix would jump from 8.3% to 9.3%.

Some of the highest sales taxes in the nation are designed to grab dollars from tourists. The New Orleans International Airport has a special 10.75% rate, while Snowmass Village, the ski resort in Colorado, levies a 10.4% sales tax. (Many locales also impose special higher taxes on services purchased by tourists, such as rental cars and hotel rooms.)

Nationally, sales taxes in 2008 generated more revenue for state and local governments–about $450 billion, a recent Government Accountability Office report suggests–than did either property taxes ($411 billion) or personal income taxes ($310 billion).

At the federal level and in some states, the income tax is progressive, with higher rates imposed on upper-income taxpayers. But rich and poor pay the same sales tax rate. In many states, however, there’s no sales tax on food or medical prescriptions.

The combined local sales rate is what local merchants charge for in-person customers. Through a parallel system called the use tax, it’s also what residents in a given jurisdiction are supposed to pay on purchases over the Internet from out-of-state sellers, but such payments are widely flouted. Congress has declined to pass legislation that would require large Internet only sellers like
Amazon.com
and
Overstock.com
to collect sales taxes for all states. (Currently, they only have to do so for states in which they have some physical presence.)

Many big online merchants, including
Wal-Mart
,
Dell
,
Office Depot Inc.
and
Staples Inc.
, collect sales taxes from Internet buyers. Some states, with New York in the lead, have adopted new “Amazon” laws designed to force the Web giant and others to collect their taxes. More such laws are likely this year.

West Virginia adopted the country’s first sales tax in 1921. Periodically, the federal government has considered a national sales tax, but such proposals have never gotten traction.

In Canada, which has a national 5% sales tax, all but two of the provinces (Alberta and Saskatchewan) have combined sales taxes of 12% or higher. The highest is the 15.5% hit on Prince Edward Island.